Phase Transition Modulation and Defect Suppression in Perovskite Solar Cells Enabled by a Self-Sacrificed Template

Tunable crystal growth offering highly aligned perovskite crystallites with suppressed deep-level defects is vital for efficient charge transport, which in turn significantly influences the power conversion efficiency (PCE) of perovskite solar cells (PSCs). Herein, a “precursor to perovskite-like template to perovskite” (PPP) growth strategy is developed, using either MAAc or GuaCl precursor to induce a sacrificial thermal–unstable perovskite-like template for (FAPbI3)x(MAPbI3)y perovskite growth. The self-sacrificed intermediate template induces the formation of highly aligned perovskite crystals with greatly enhanced film crystallinity and suppresses deep-level defect formation. Furthermore, it is proved that MAAc or GuaCl completely evaporates during the high-temperature annealing process. The reduction in defect densities and nonradiative recombination enhances both carrier lifetime and charge dynamics, yielding impressive PCEs of 22.3% and 22.8% with a high open-circuit voltage (VOC) of 1.16 V and an incredible fill factor (FF) of 81.5% and 79.4% for MAAc- and GuaCl-based devices, respectively. These results suggest that the formation of the thermal–unstable perovskite-like sacrificial template is a promising strategy to restrain the deep-level defects in perovskite films toward the attainment of highly efficient and stable large-scale PSCs as well as other perovskite-based electronics.